1. Field of the Invention
The present invention generally relates to particulate material flow monitoring assemblies and particularly to particulate material flow monitoring assemblies which indicate not only proper fuel flow in a chute but upstream and downstream chute blockage conditions.
2. Description of the Prior Art
Certain boilers especially in saw mills are fueled by particulate fuel materials such as wood, sawdust and bark chips. Such fuel is known as hogged fuel. Generally the hogged fuel is fed from conveyors into inclined chutes leading to the boiler. At the conveyor end of the chute a paddle wheel or other control feeder arrangements feed the hogged fuel into the chute while another paddle wheel or other fuel distributor arrangement at the opposite end of the chute feeds the hogged fuel into the boiler. Because of the moisture content of the hogged fuel, sometimes 65%, the particulate material tends to lump together and clogs either the upstream conveyor paddle wheel or the downstream boiler feed paddle wheel. Thus the condition of the chute had to be monitored to insure that proper hogged fuel flow is maintained to the boiler.
Prior art monitoring included the placement of a window in the chute through which an operator visibly checked chute conditions. Light sources and receiver-detectors were also placed at opposite window ends of the chute and the intensity of the light was monitored by the receiver to determine proper fuel flow. However, the light detectors produced a D.C. signal proportional to the amount of light that was transmitted. Over a period of time the windows through which the light shines tended to get dirty and consequently the D.C. level would drop and get to a point below the alarm point of the D.C. detector setting off a false alarm condition.
Thus what was needed was an automatic hogged fuel monitoring assembly which would not be affected by dirty chute windows and which would provide a signal indicative of proper chute fuel flow and upstream and downstream chute blockage conditions.